Paper drive system



S. P. MABON July 1, 1969 PAPER DRIVE SYSTEM Filed Oct. 10, 1966 POSITION PULSE Y T C O L E V PAPER E m T F|G.2(b)

w 4 IIIIVIIIJ 6 7 mm F 4 9 T1 E M M L 6 O 2 8WD H 6 w m O m T EP 2 VAKI7 4 1 H t 2 W5 w M JL 0 Fm Q M O 00] 4 FLCC F h 8 .IO 7 W 0 C O! O 8 PP 6 D E C MR 6 MUA 00 CS INVENTOR. STUART P. MASON FIG; ---3 July 1, 1969 s. P. MABON PAPER DRIVE SYSTEM Sheet Filed Oct. 10, 1966 'INE iggCOUNTER IDECREMENT PICKOFF 90 AMP FIG. 4

INVENTOR.

STUART P. MABON ATTORNEYS United States Patent 3,452,853 PAPER DRIVE SYSTEM Stuart P. Mabon, Santa Monica, Calif., assignor to Data Products Corporation, Culver City, Calif, a corporation of California Filed Oct. 10, 1966, Ser. No. 585,666 Int. Cl. B41j 15/00; B65h 25/32, 25/02 US. Cl. 197-133 11 Claims ABSTRACT OF THE DISCLOSURE A system particularly useful for incrementally driving paper past a printing hammer bank. The system includes a motor mechanically coupled to the paper. A velocity servo loop is provided to establish and maintain a predetermined motor velocity. Position sensing means are provided to sense the position of the motor shaft and to initiate a controlled deceleration of the motor shaft from a known position and a known velocity.

This invention relates generally to means for driving paper and the like past a printing or other operational station and finds particular utility in line printers for incrementally driving paper pasta printing hammer bank.

Line printers which are often used with digital data processing equipment as output devices, include a printing station usually consisting of a plurality of aligned hammers or electrodes. A paper strip is usually incrementally driven past the printing station so that a full line of printing is performed each time the strip comes to rest. Although present state of the art printers are capable of very fast operation, on the order of one thousand or more lines per minute, attempts to even further increase the speed are oftentimes restricted by the rate at which the paper can be driven. That is, it is necessary after each line of printing to move the paper and permit it to settle in its new position before a subsequent line can be printed if aligned symbols and generally neat printing are to be achieved.

In order to move paper very rapidly, it is common practice to very quickly introduce a great amount of energy into the paper drive system as by actuating an electromagnetic clutch to couple the paper tractor shafts to a reservoirof mechanical energy. Deceleration is accomplished by releasing the clutch and applying a brake. Control over the application of torque, which is extremely important in high speed operation, to eliminate a long settling time, is difficult to obtain since the time constants of the devices are normally too large to allow the rapid changes of torque that are necessary. In addition, the clutch-brake system suffers from the wear of mechanical parts resulting in changes in characteristics. To illustrate this point, a magnetic particle clutch with suitable torque capability and a rated life of five million operations, allows for two weeks operation of a one thousand line per minute machine, running for forty hours per week. Hydraulic systems and stepping motor systems have also been employed, but these require additional mechanical or electronic components in order to satisfactorily stop paper after a rapid increment.

In view of the shortcomings of known prior art apparatus, it is an object of this invention to provide an improved system for rapidly moving paper and the like.

Briefly, paper is rapidly and precisely moved in accordance with the present invention by providing a servo loop to establish a predetermined velocity of the paper from which a controlled deceleration is initiated in response to a position indicating pulse.

, In accordance with a preferred embodiment of the at an increased velocity,

invention, a direct current permanent magnet printed armature motor is employed. A velocity servo loop is utilized which includes a direct current tachometer as the velocity measuring element. The tachometer output is fed back to the input of an amplifier driving the motor. Position information is provided by a magnetic pickoff in conjunction with an aluminum disc, mounted on the motor shaft, in which are embedded small iron inserts at 15 intervals around the circumference thereof. (The motor shaft rotates 15 for each line increment.)

When the paper is required to step one line, the command voltage is applied to the servo input and the motor, tractors, and paper accelerate to a velocity proportional to the input voltage level. Soon after reaching this velocity, the position disc induces a voltage in the pickolf element which initiates deceleration.

Although the use of a velocity servo system in a paper movement apparatus has many advantages over prior art techniques, a pure velocity servo system of course has little resistance to drift when at zero velocity and accordingly hammer impact could move the paper in either a forward or reverse direction. Therefore, in accordance with a significant feature of the present invention, an overrunning clutch is utilized to prevent motor rotation drift in a reverse direction. In order to prevent drift in a forward direction, a small current is provided to the motor when in its rest condition which supplies a reverse torque causing the clutch to engage.

In accordance with a further feature of the present invention, in order to slew the paper, i.e., to move it several lines at a time, means are provided for rotating the motor e.g., double the normal velocity. In order to stop the motor, its velocity is reduced to normal when the penultimate line is reached and then reduced to zero when the ultimate line is positioned.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in connection with the accompanying drawing, in which:

FIGURE 1 is a schematic illustration generally showing the mechanical features of a system in accordance with the present invention;

FIGURES 2(a) and 2( b) illustrate a pair of waveforms generally representing the operation of a motor in accordance with the present invention;

FIGURE 3 is a block diagram illustrating the electrical configuration of a system in accordance with the present invention;

FIGURE 4 is a block diagram illustrating in greater detail the logic circuit of FIGURE 3; and

FIGURE 5 is a schematic diagram illustrating in greater detail the waveshaping circuit of FIGURE 3.

Attention is now called to FIGURE 1 of the drawing which illustrates the mechanical features of a paper drive system in accordance with the present invention. Such a system is employed in line printers for example for incrementally moving the paper past a printing station. Normally, the paper is moved one line at a time in a step mode. However, most line printers also are capable of operating in a slew mode in which the paper can be moved through several lines.

FIGURE 1 illustrates a typical strip of paper 10 adapted to be utilized in line printers. The paper 10 is moved past a printing station (not shown) which for example can be comprised of a bank of individually actuable impact hammers. Usually, the bank will include a number of hammers equal to the maximum number of characters to be printed in any one line. A printing ribbon will normally be disposed between the paper 10 and the hammer bank. A character drum normally rotates adjacent the rear surface of the paper 10. The character drum usually defines a plurality of tracks equal in number to the number of hammers in the bank. In order to print a particular character at a desired position in a line, the hammer associated with that position is propelled against the drum when the character to be printed is aligned with it. As a consequence, the printing ribbon and paper are moved against the drum, resulting in the character being printed on the front surface of the paper. After all of the characters in a line have been printed, the paper strip is stepped so that the next line can then be printed. In order to enable lines to be printed at a rate greater than one thousand per minute, it is of course necessary that the paper be stepped and stopped very rapidly. If printing is initiated before the paper settles, a very poor quality print will of course result. A system in accordance with the present invention is intended to very rapidly move and quickly and precisely stop the paper.

As is conventional practice, the paper is provided with a series of holes 12 which run along both edges thereof. The paper 10 runs through guides 14 and is driven by tractor wheels (not shown) engaged with the holes 12. The tractor wheels are carried by tuactor shafts 16 and 18 which are mounted for rotation between brackets 20 and 22. The tractor shafts 16 and 18 are respectively driven by webbed belts or the like 24 and 26. The belts 24 and 26 are in turn driven by a shaft 28.

The apparatus recited thus far is substantially conventional in nature. The present invention is primarily directed toward an improved system for controlling the rotation of the shaft 28 in order to rapidly and precisely drive the paper 10. In accordance with the present invention, the shaft 28 constitutes the shaft of a motor 30. Preferably, though not necessarily, the motor 30 comprises a direct current permanent magnet printed tarmature motor. A typical motor of this type is manufactured and sold by Photocircuits, Glen Cove, N.Y., under model No. U12C. Such motors can normally be driven in either a forward or reverse direction depending upon the polarity of the signal applied to the motor terminals 32 and 34. In order to prevent backlash when the motor 30 is rapidly stopped, an overrunning clutch 36 is coupled to the motor shaft 28. The overrunning clutch 36 functions to prevent motor rotation in one direction, i.e., a reverse direction, while freely permitting rotation in the forward direction. A suitable overrunning clutch is manufactured and sold by Miniclutch, Hamdon, Conn., under model No. HU7.

Also coupled to the shaft 28 is a disc 38 which enables the shafts position to be determined by a position pickoff transducer 40. Preferably, the disc 38 is formed of aluminum and has iron inserts 42 disposed therein around the periphery thereof at equal intervals. For example, if the spacing between lines to be printed on the paper 10 is equivalent to a rotation of the shaft 28, thenthe disc 38 will have iron inserts 42 disposed therein at 15 intervals. The position pickoif transducer 40 can comprise a conventional magnetic pickup which senses the proximity of the low reluctance magnetic inserts 42. Also connected to the shaft 28 is a tachometer 44. Preferably, the tachometer 44 provides a direct current output voltage on its terminals 46 and 48 which is linearly related to the shaft velocity 28.

Attention is now called to FIGURES 2(a) and 2(b) which are comprised of waveforms generally illustrating the concept of the operation of a system in accordance with the present invention. More particularly, FIGURE 2(a) comprises a plot of shaft or paper velocity versus time. Let it be assumed at time t a command signal is generated which is intended to move the paper 10 through one line. In accordance with the present invention, the shaft 28 is accelerated to increase its velocity or rotational speed from zero to a first predetermined level S1. This acceleration is represented by the ramp portion 50 of the curve of FIGURE 2(a). It is to be understood however that the shaft 28 need not be accelerated along the line 50 but indeed the acceleration could be at other rates as for example represented by dotted line ramps 52 and 54. The advantage of following dotted line ramp 52 for example (as opposed to ramps 50 and 54) is that the shaft 28 can be moved to its next position more rapidly inasmuch as will be seen a greater porition of its cycle time is spent at a higher velocity. The disadvantage of traversing a sharp ramp 52 is that longer life can be assured in any mechanical system by minimizing the magnitude of acceleration. Contrariwise, the disadvantage of following a ramp such as is represented by line 54 is that the paper 10 cannot be stepped as rapidly but longer maintenance-free life is probably assured. Ramp 50 represents somewhat of a compromise between ramps 52 and 54. In addition, the slope of ramp 50 is illustrated as being identical with the slope of a negative acceleration or decelerating ramp 56 which can enable certain circuit economies to be taken advantage of.

Regardless of which particular acceleration path (50, 52, or 54) is followed, the shaft 28 is positively accelerated from time t from a velocity of zero to the predetermined velocity S1. As previously noted, the velocity S1 is maintained by a velocity servo system to .be discussed in greater detail hereinafter. At some subsequent time, e.-g., t the position pickoif transducer 40 will provide a pulse in response to the next iron insert 42 moving into proximity therewith, indicating that the shaft 28 is almost properly positioned. In response to the pulse, the shaft 28 is thereafter negatively accelerated along ramp 56. Since the position and velocity of the shaft 28 is known at the time the position pulse is generated by the transducer 40, and since the slope of deceleration as represented by the ramp 56 is known, the velocity of the shaft 28 should reach zero (as at time t when the shaft 28 is in proper position, i.e., the paper 10 is properly oriented with respect to the printing station for the next line to be printed.

It is to be noted that the area under the curve of FIGURE 2(a) between times t and 1 represents the integral of velocity with respect to time or in other words the distance that the paper 10 travels subsequent to the time the position pulse is generated. Since the generation of the position pulse is a reference, the only error that can be introduced in the ultimate position at which the paper 10 stops is introduced between times t and t Inasmuch as the distance traveled between times t and t normally represents only a small fraction, e.g., one-third, of the total distance traveled in a single step, i.e., between times t and t then the effect of any percentage error introduced during stopping between times t and t has a lesser effect on the total stepping distance. In other words, if a ten percent error in the stopping distance is introduced between the time the position pulse is generated and zero velocity is achieved, this error will result in only a three percent (10% 3) error in the total paper step.

Whereas FIGURE 2(a) generally illustrates the operation of a system in accordance with the present invention in order to move the paper 10 through a single step, the curve of FIGURE 2(b) illustrates the operation when the paper 10 is moved in a slew mode, i.e., moved through two or more steps. In this situation, the shaft 28 is accelerated, as along ramp 60, until it reaches a second predetermined velocity S2. The velocity servo system then maintains the velocity S2 while the number of lines to be skipped is decremented each time a pulse is provided by the transducer 40. When the penultimate line is reached, the position pulse generated by the transducer 40 as at time t will decelerate the motor 30 along ramp- 62 to velocity S1. When the next position pulse is recognized as at time t the shaft 28 will be decelerated along ramp 64 down to a zero velocity at time t From the foregoing, it should be appreciated that in accordance with the present invention, a drive member,

such as shaft 28, driving a load, such as paper 10, is positively accelerated up to a predetermined velocity at which it is maintained by a velocity servo means. After a pulse is generated in response to the drive member 28 reaching a reference position, the drive member 28 is negatively accelerated or decelerated in order to reduce its velocity from the predetermined level to zero. An electrical configuration for controlling the shaft 28 in accordance with the curves of FIGURES 2(a) and 2(b) is illustrated in FIGURE 3.

A logic control circuit 70 is shown in FIGURE 3 which controls, through a waveshaping circuit 72, an amplifier 74 driving motor 30. The logic control circuit 70 is responsive to signal information provided by a command source 76. Thus, the command source 76 can command a single step movement of the paper as for example providing a true logical level on line 78. In order to command a multistep paper movement, a true logical level is provided on line 78 and the number of lines to he stepped is represented by information provided on line 80.

Assume for example that the paper 10' is to be moved through a single step. As a consequence, the command source 76 will provide a pulse on line 78 to the logic control circuit 70 to switch it to a true state as represented by the step 82 in signal 84 illustrated at the output of the logic control circuit 70. In response to this step 82, the Wave-shaping circuit 72 will provide a ramp signal 86 to the amplifier 74 to thus accelerate the motor 30 from a zero velocity toward the velocity S1. The motor shaft 28, as previously noted, is coupled to the tachometer 44 and the position pickofi transducer 40. The output of the tachometer 44 is coupled back to the input of amplifier 74. Accordingly, in response to the ramp signal 86, the motor shaft 28 will be driven to the predetermined velocity S1 and will be maintained there as a consequence of the feedback through the shaft 28 to the tachometer 44 to the amplifier 74. It will be appreciated that this configuration comprises a conventional feedback servo 100p.AS is well known to those skilled in the art, by properly choosing the characteristics of the feedback loop, the velocity of the shaft 28 can be maintained at the desired level inasmuch as if it increases above a value set by the input signal, then an error signal will be provided to the amplifier to change the shaft velocity to correspond to that dictated by the input signal.

The output of the position pickoff transducer 40 is coupled through an amplifier 90 to the input ofthe logic control circuit 70 to switch the circuit 70 back along step 92 when the reference position" of the shaft 28 is recognized during the last step of the paper movement. The step 92 causes the wave-shaping circuit 72 to provide a ramp output signal 94 to decelerate the motor 30 in the manner previously disclosed; i.e., along the ramp 56 as shown in FIGURE 2(a).

Attention is 'now called to FIGURE 4 which comprises a block diagram illustrating a typical configuration for the logic control circuit 70 of FIGURE 3. The logic control circuit 70 includes first and second flip-flops 100 and 102 which can be considered to be of the conventional set/ reset type. The step input line 78 from the comthrough more than one line, the flip-flop 102 is set through AND gate 104. If the counter 106 defines a count of one, then the decoder 108 will provide a true output signal on its output line 112. The output line 112 is connected to the input of AND gate 114 whose output is connected to the reset input terminal of flip-flop 102. The false output terminal of flip-flop 102 is connected to the input of AND gate 116 connected to the reset input terminal of flip-flop 100. The output of the pickolf amplifier 90 (previously shown in FIGURE 3) is connected to the input of AND gates 114 and 116 and in addition is connected to a decrement input terminal of the counter 106.

In the operation of the logic control circuit 70 of FIGURE 4, consider initially that a single step command is provided by the command source 76. In this event, only the flip flop 100 will be set. As will be described in greater detail hereinafter, the waveshaper 72 will provide a ramp output signal to a voltage level Va which accelerates the shaft to the velocity $1 in response to the flip-flop 100 switching true. When the shaft 28 moves sutficiently to induce a pulse in the magnetic pickup 40, the pulse will be transferred by the pickoff amplifier 90 to the AND gate mand source 76 is connected to the set input terminal of flip-flop 100. The true output terminals of the fiip fiops 100 and 102 are respectively connected through lines 101 and 103 to input terminals of the wave-shaping circuit 72. In addition, the true output terminal of flip-flop 100 is connected to the input of an AND gate 104 whose output is connected to the set input terminal of the flip-flop 102. The line count input line 80 from the command source 76 is connected to the input of a counter 106 whose output is connected to the input of a decoder 108.'In the event the counter 106 stores a count greater than one, a true output signal is provided on decoder output line 110- connected to the input of AND gate 104. Thus, if the flipfiop 100 is set and the counter 106 stores a count greater than one, indicating that the paper 10 has to he stepped 116. Assuming that the flip-flop 102 had not been set, it will still define a false state and as a consequence, the flipflop 100 will be reset to thereby initiate the voltage ramp 94 shown in FIGURE 3 to in turn decelerate the motor 30 along the ramp 56 shown in FIGURE 2(a). Assume now that a multistep command is provided by command source 76. In this case, the number of lines to be stepped is loaded into the counter 106 through line 80. Thus, when the flip-flop 100 switches true, it will enable gate 104 such that flip-flop 102 will be set as a consequence of the counter 106 providing a count greater than one. As will be seen hereinafter, in response to both input terminals of the wave-shaper 72 being true, it will provide an output voltage ramp which increases to a greater voltage Vb (e.g., Vb=2 Va) than is employed for the single step command. Thereafter, the velocity servo loop will maintain the shaft velocity at the second predetermined velocity S2.

As the shaft 28 rotates, for each line, the pickotf amplifier will provide a decrementing pulse to the counter 106. When the counter 106 is stepped down to a count of one, the decoder output line 112 will go true so as to reset the flip-fiop 102 when the next pulse is provided by the pickolf amplifier 90. As a consequence, flip-flop 102 is reset and as will be seen hereinafter, the output of the wave-shaping circuit 72 will reduce to the first voltage level Va corresponding to the first predetermined velocity S1. In response to the next line position of the shaft 28, the pickolf amplifier 90 will provide a pulse through gate 116 to reset the flip-fiop to thereby reduce the voltage output of the wave-shaper 72 along a ramp to a zero value to therefore negatively accelerate the shaft 28 as along a ramp 64 in FIGURE 2(b).

Attention is now called to FIGURE 5 which illustrates a circuit diagram of a typical wave-shaping circuit 72 which possesses the previously described operational characteristics. Thus, the wave-shaping circuit 72 of FIGURE 5 is comprised of a first constant current source 120 consisting of a variable resistor 122 connected between the emitter of an NPN transistor Q1 and a source of negative potential, nominally 20 volts. A zener diode 124 is connected between the source of negative potential and the base of transistor Q1. The base of transistor Q1 is connected through a resistor 126 to ground. The collector of transistor Q1 constitutes the output terminal of the con stant current source and it is connected through a pair of serially connected Zener diodes 128 and 130. The collector emitter path of a PNP transistor Q2 is connected across the Zener diodes 128 and 130. The base of transistor Q2 is connected through a resistor 132 to the previously mentioned true output terminal 101 of flip-flop 100. The collector emitter path of PNP transistor Q3 is connected across the Zener diode 130. The base of transistor Q3 is connected through a resistor 134 to the true output terminal 103 of flip-flop 102.

The collector of transistor Q1 is connected through a diode 136 to a capacitor 138 and to the base of a PNP transistor Q4 connected in an emitter follower configuration. That is, the collector of transistor Q4 is connected through a resistor 140 to the source of negative potential previously mentioned. The emitter of transistor Q4 is connected through a resistor 142 and a diode 144 to the source of ground potential previously mentioned.

Also connected to the upper terminal of capacitor 138 is a second constant current source 146 substantially identical to the constant current source 120. More particularly, constant current source 146 includes a PNP transistor Q whose collector is connected to the upper terminal of capacitor 138. The emitter of transistor Q5 is connected through a variable resistor 148 to a source of positive potential, nominally shown as +20 volts. A Zener diode 150 is connected between the base of transistor Q5 and the source of positive potential. A resistor 152 is connected between the base of transistor Q5 and the previously mentioned source of ground potential.

A movable tap 154 associated with the resistor 142 connected to the emitter of transistor Q4 is connected to the base of a PNP transistor Q6 whose collector is connected through a resistor 156 to the previously mentioned source of negative potential. The emitter of transistor Q6 is connected through series resistors 158 and 160 to the source of ground potential. A capacitor 161 is connected in parallel with the resistors 158 and 160. The junction between the resistors 158 and 160 is connected through a resistor 162 to the source of positive potential.

In the operation of the circuit of FIGURE 5, initially assume that when the flip-flops 100 and 102 define false states, they provide negative voltages, e.g., -5 volts on their true output terminals 101 and 103. On the other hand, assume that when the flip-flops 100 and 102 switch true, they provide positive output voltages on the terminals 101 and 103. Accordingly, when the flip-flops 100 and 102 are in their false state, transistors Q2 and Q3 are both conducting. Accordingly, a substantially ground potential will be established at the collector of transistor Q1. As a consequence, transistors Q4 and Q6 will be held off such that the output terminal, i.e., the emitter of transistor Q6 will also be at substantially ground potential. Now assume that a single step command is provided meaning the flipflop 100 switches true thereby providing a positive potential On line 101 to cut transistor Q2 off. Transistor Q3 remains on. Thus the potential established at the collector of transistor Q1 will be equal to the reverse voltage drop across the Zener diode 128. As a consequence, the capacitor 138 will charge to the level established by the Zener diode 128 at the collector of transistor Q1. The transistor Q4 will therefore conduct driving the potential on its emitter and the tap 154 negative. Consequently, the output appearing on the emitter of transistor Q6 will also be driven negative to define the ramp 164 whose slope will be determined by the charging time constant of the circuit including capacitor 138. The setting of the variable resistor 122 will determine the rate of charge or the slope of the ramp 164. The setting of tap 154 on resistor 142 will determine the magnitude of output voltage to be established on the emitter of transistor Q6. When the pickoff amplifier 90 provides a pulse to reset the flip-flop 100, the transistor Q2 will start conducting again and the capacitor 138 will recharge from the constant current source 146 to thereby establish the output ramp 166 whose slope is determined by the setting of variable resistor 148.

In the case of a \multistep command, both transistors Q2 and Q3 will be cut off, thereby establishing a voltage at the collector of transistor Q1 determined by the serial drop across Zener diodes 128 and 130. Accordingly, the capacitor 138 will charge to twice the voltage to which it was charged in the case of a single step command. Its rate of charge or time constant will however be the same assuming the value of resistor 122 has not been adjusted. As previously described in conjunction with FIGURE 4, the velocity of the shaft 28 is reduced in increments as shown in FIGURE 2(b) as by initially resetting the flip-flop 102 (to thus initially permit transistor Q3 of FIGURE 5 to start conducting) and to thereafter reset flip-flop 100 to subsequently permit transis tor Q2 to start conducting.

As will-be apparent to those skilled in the art, utilization of a velocity servo system as disclosed herein provides very little resistance to drift when the paper 10 is at rest. As a consequence, the impact of the hammers against the paper 10 during printing can move the paper 10 in a forward direction. The hammers will not of tion, a small bleed current is provided to the motor 30 when in its rest state to provide a reverse torque which engages the overrunning clutch 36 .and locks the motor 30. This bleed current is provided to the output terminal connected to the emitter of transistor Q6 through resistor 162. Thus as can be seen in the waveform illustrated at the output terminal of the circuit of FIG- URE 5, when a voltage for driving the motor is not being provided, a small bleed current as shown at 168 is being provided to introduce the reverse torque for locking the motor 30.

From the foregoing, it should be appreciated that a drive system has been disclosed herein suitable for drivmg paper 10 in a line printer apparatus. To summarize briefly, a system in accordance with the invention employs a velocity servo system together with a position pickoff means in order to smoothly and rapidly decelerate a drive member 28- at a prescribed rate from a known position and velocity to bring the drive member 28 to rest precisely and rapidly. Moreover, in accordance with the invention, an overrunning clutch 36 is provlded to prevent any backlash of the drive member 28 when it is being stopped. In addition, the overrunning clutch 36 is utilized to positively lock the drive member 28 when in its rest position. In addition, it should be appreciated that the system disclosed herein is applicable ftor movmg the paper 10 in both single and multiple s eps.

What is claimed is:

1. A drive system for precisely physically moving a load through one or more increments, each increment comprrsmg a known distance, said system comprising:

.a drive member coupled to said load;

drlve means including motor means fixedly coupled to sa1d drive member;

circuit means for applying signal energy to said motor means for accelerating said drive member from a zero velocity and servo loop means for establishing and maintaining said drive member at a preselected velocity;

position sensing means for providing a pulse in response to said drive member reaching a predetermined position; and

means responsive to said pulse for causing said circu1t means to apply signal energy to said motor means to decelerate said drive member from said preselected velocity at a controlled rate.

2. The system of claim 1 wherein said drive member comprises .a rotatable shaft of said motor means; and wherein said circuit means further includes means for applying ramp signals to said motor means to respectively accelerate and decelerate said drive member.

3. In a high speed printing apparatus, a system for rapidly and precisely moving paper, said system comprising:

a drive motor including a rotatable shaft;

means directly coupling .said shaft to said paper;

circuit means for .applying signal energy to said motor to selectively either positively or negatively accelerate said shaft at a controlled rate;

means capable of defining a single step paper movement command;

control means responsive to the definition of said single step command for causing said circuit means to positively accelerate said shaft from a zero to a first preselected velocity;

sensing means for sensing the position of said shaft;

said control means further including means coupled to said sensing means and responsive to said shaft reaching a predetermined position for causing said circuit means to apply signal energy to said motor to negatively accelerate said shaft at a controlled rate from said first preselected velocity to said zero velocity.

4. The apparatus of claim 3 including servo means for regulating the velocity of said rotatable shaft.

5. The apparatus of claim 4 wherein said servo means includes a tachometer coupled to said shaft.

6. The apparatus of claim 3' wherein said sensing means includes elements carried by said shaft spaced around the periphery thereof; and

means for recognizing said element.

7. The apparatus of claim 3 wherein said drive motor comprises a reversible motor; and

clutch means for preventing rotation of said shaft in a first direction.

8. The apparatus of claim 7 wherein said circuit means includes means applying signal energy to said motor tending to drive it in said first direction when said shaft velocity is zero.

9. The apparatus of claim 3 wherein said circuit means includes means for generating a ramp signal having a References Cited UNITED STATES PATENTS 2,783,427 2/1957 Bracutt 318398 X 2,800,073 7/1957 Block 197133 X 2,825,620 3/1958 Sperry et al 197-433 X 2,842,249 7/ 1958 Morgan et a1 197133 2,842,250 7/1958 Furman et al 197-133 2,884,852 5/1959 Saltz 1 97-133 X 3,014,570 12/ 1961 Cunningham 197--133 3,043,589 7/1962 Folmar 197133 X 3,094,261 6/1963 Thompson 197-133 X 3,123,195 3/1964 Hewitt et al. 197-133 3,284,688 11/1966 Black 318326 X 3,345,008 10/1967 Jacoby 318326 X 3,356,200 12/1967 De George 197-133 X ERNEST T. WRIGHT, IR., Primary Examiner.

US. Cl. X.R. 

